Cholesterol facts

A high level of cholesterol is one of the factors that can
increase your risk of cardiovascular disease, eg
angina,
heart disease and
stroke.

This is because high levels of cholesterol lead to fatty
deposits that cause the arteries to narrow (atherosclerosis) and
restrict blood flow to the heart. This is one of the key causes of
cardiovascular
disease.

What is cholesterol?

Cholesterol is an important substance that's used by the body
in many ways.

It's the starting point of manufacture for many of the body’s
natural steroid hormones and for vitamin D, which controls calcium in the
body.

It is also an essential component of the membrane that forms the
walls of individual cells in all tissues.

Eighty per cent of the cholesterol we have is produced within
our own body – mostly by the liver. It's then transported from the liver via
the blood stream to other tissues.

Cholesterol travels through the blood in minute packages mixed
with large molecules called lipoproteins. Lipoproteins are themselves
combinations of
fats and
proteins.

Fats, such as cholesterol, don't dissolve well in the blood
stream, but they become soluble when coated with lipoproteins.

What are lipoproteins?

Four main groups of lipoproteins exist, based mainly on their
different sizes and density:

high-density lipoproteins (HDL)

low-density lipoproteins (LDL)

very low-density lipoproteins (VLDL)

chylomicrons.

Each group has a different function in the body.

How do they affect cardiovascular health?

High-density lipoproteins (HDL) mop up excess
cholesterol in the body and return it to the liver for re-processing. HDL is
often called good cholesterol and raised levels give
protection against heart disease.

Low-density lipoproteins (LDL) transport
cholesterol from the liver to be deposited elsewhere in the body. LDL is known
as bad cholesterol because it deposits cholesterol in the
lining of your arteries. The more LDL you have, the more likely you are to
develop heart disease.

What affects levels of lipoproteins?

Men generally have higher levels of LDL compared to
women.

This is probably because of the protective effect of oestrogen,
one of the female hormones. Following the
menopause, this
difference disappears.

Exercise raises HDL levels, as does modest alcohol intake.

Why test cholesterol?

Every adult should have it measured at least once when they are
in their thirties, and then every 5 years.

This is particularly important if you have other major risk
factors for coronary disease, such as
smoking or
diabetes.

Cholesterol is easily measured in a blood sample. If high
cholesterol runs in your family, it's better to measure cholesterol at a much
younger age – some time in your 20s.

Cholesterol levels don't tend to fluctuate, so if you have a
normal level it doesn't need to be repeated often, but should be rechecked at
least every five years, or more often if you develop diabetes or
high blood
pressure.

If it's high, it may need quite frequent re-testing to gauge the
effect of treatment.

You could also purchase a cholesterol monitoring kit and strips
so that you can record your readings at home and then be able to discuss them
with your GP at your next appointment.

What do the figures mean?

Total cholesterol

This is the single figure for your cholesterol level, which is
all the subtypes combined.

The desirable upper limit of total cholesterol (TC) for people
who have diabetes is 4mmol/l.

As with the other risk factors for cardiovascular disease,
raised cholesterol is of more concern if there are other factors
present:

someone who has a TC of 6mmol/l, but is fit, is not
overweight, has no family history of heart disease and doesn't have
diabetes or
smoke and is less than 60 years old
will have little or no benefit from lowering their cholesterol

someone with the same cholesterol level but who smokes, is
overweight and has
high blood pressure
will reduce his cardiovascular risk quite a lot by getting his cholesterol
down.

Age itself is such a major risk factor for coronary disease
that most people over 70 need to reduce their levels, unless the cholesterol
levels are very low.

Perhaps the best way to think about cholesterol level is to
consider the bodies resistance to damage from cholesterol; when you are young
without ill-health, your body is very resistant to even quite high levels of
cholesterol.

Increasing age, diabetes and smoking all reduce the bodies
resistance to cholesterol attack, as does high blood pressure, and men are more
sensitive to cholesterol attack than woman.

This information can all be put into risk prediction charts,
allowing one to calculate how dangerous any given cholesterol level is in a
particular individual.

This information can also be used to work out how to reduce
the danger.

The commonest means to reduce danger is to reduce cholesterol,
but danger can be reduced by stopping smoking, reducing blood pressure, taking
more exercise and if relevant improving diabetic control.

Cholesterol treatment and diabetes

Statins should be prescribed as primary prevention in all
diabetic patients over 40 years old with a TC of more than 4mmol/l or and
LDL-cholesterol of more than 2mmol/l.

Statins may be prescribed to younger diabetic patients if
there are additional risk factors for cardiovascular disease or there is
evidence of
diabetic eye disease
(retinopathy) or
diabetic kidney
disease (nephropathy).

All diabetic patients with a history of
heart attack,
stroke or
cardivascular disease should be prescribed a statin to preven further attacks
(secondary prevention).

Some people find they are intolerant of statins and experience
side-effects, such as muscle pains,
fatigue and nausea.

If that occurs, there are a number of prescribable
alternatives – such as
ezetimibe or
fibrate drugs, which may not cause these problems.

References

National Institute for Health and Care Excellence. The
management of Type 2 diabetes (update). www.nice.org.uk/CG66

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